Question: Simplify to lowest terms. $\dfrac{20}{45}$
Solution: What is the greatest common factor (GCD) of 20 and 45? $20 = 2\cdot2\cdot5$ $45 = 3\cdot3\cdot5$ $\mbox{GCD}(20, 45) = 5$ $\dfrac{20}{45} = \dfrac{4 \cdot 5}{ 9\cdot 5}$ $\hphantom{\dfrac{20}{45}} = \dfrac{4}{9} \cdot \dfrac{5}{5}$ $\hphantom{\dfrac{20}{45}} = \dfrac{4}{9} \cdot 1$ $\hphantom{\dfrac{20}{45}} = \dfrac{4}{9}$